The JHS represents an expansion of the Jackson Field Center of the Atherosclerosis Risk in Communities (ARIC) study, to broaden data collection in an African American population and to increase access to and the participation of African American populations and scientists in biomedical research and professions. A total of 15,792 individuals were initially examined for ARIC, of which 3,732 were enrolled at the Jackson site. When the JHS began, it invited all previous Jackson ARIC participants, who were approximately 59 to 78 years of age, along with younger and older African American residents from a larger Jackson geographic area, to participate in the new cohort study. Due to JHS shared cohort membership with ARIC, the two studies cooperate with each other in data analysis and on events validation for members of the two cohorts through a subcontract from the JHS Coordinating Center to the ARIC Coordinating Center at the University of North Carolina.